Drive mechanism for vacuum switches



May 15, 1962 w. N. LINDSAY DRIVE MECHANISM FOR VACUUM SWITCHES Filed July 18, 1960 his Attorney United States Patent 3,035,139 Patented May 15, 1962 3,035,139 DRIVE MECHANISM FOR VACUUM SWITCHES Wesley N. Lindsay, San Jose, Calif., assignor, by mesue assignments, to Jennings Radio Manufacturing Corporation, San Jose, Calif., a corporation of Delaware Filed July 18, 1960, Ser. No. 43,382 3 Claims. (Cl. 200-111) This invention relates to vacuum switches and more particularly to a drive mechanism for opening and closing the switch contacts without the use of moving shafts or complicated seals or bellows.

In vacuum switches of high capacity it is desirable to close the switch contacts as quickly as possible to prevent arcing and, at the same time, it is necessary to retain the switch points in contact with a relatively high force so as to insure an efficient current flow.

The principal object of this invention is the provision of a drive mechanism for vacuum switches of simple design and of relatively low mass thereby permitting high speed actuation of the movable contact.

Still another object of the invention is the provision of I a drive mechanism for vacuum switches which is mechanically guided so that the frictional resistance to movement is minimized.

Other objects and advantages of the invention will be apparent from the following specification and from the drawings. The attached drawings and specification are illustrative of a preferred embodiment of the invention and it will be understood that various modifications may be resorted to by those skilled in the art without departing from the scope of the appended claims.

FIG. 1 is a fragmentary vertical half section through a vacuum switch embodying the invention and showing only the lower portion of a typical vacuu-mized envelope.

FIGS. 25 are cross sections of the invention at various points along the length of the switch indicated by corresponding section lines in FIG. 1.

In terms of broad inclusion the present invention provides a movable switch contact supported on an armature within the vacuumized envelope and which armature is adapted to be reciprocated in one direction by the magnetic field of a coil positioned outside the envelope. A helical spring is provided for urging the armature in the opposite direction when the coil is deenergized. In the following description of a preferred form of the invention the magnetic attraction of the coil opens the switch and the spring closes it. However the reverse operation is also contemplated.

In detail, and with reference to FIG. 1 a portion of the envelope containing the vacuumized switch is generally indicated at 1. A fixed contact 2 is secured to the euvelope 1 in any suitable manner (not shown) so that said fixed contact may be engaged by the movable contact 3 to close the circuit involved.

Movable contact 3 may be fixedly secured to one end of a tubular element 4 which is soldered or otherwise secured at its opposite end to a generally cylindrical armature 5. The armature 5 is adapted to reciprocate in a complementarily formed socket generally designated 6.

Socket 6 is formed within a tubular switch housing 10 of magnetic material which may also function as a terminal of the switch. Said housing 10 is connected by means of an annular copper skirt 11 to the envelope 1 as clearly shown in FIG. 1.

At the end of housing 14 adjacent envelope 1 (that is, the vacuumized end) it is provided with a relatively small diarneter bore 12 in which armature 5 is reciprocable. The opposite or outside end of housing 10 is provided with a relatively large diameter bore 13 which receives therein a magnetic coil 14 adapted to attract armature 5 from the position shown in FIG. 1.

A reduced diameter counterbore 17 is formed in housing 10 and is adapted to receive therein the open end of a sealin cup 18 of nonmagnetic material. The closed end 19 of cup 18 extends into the larger bore 13 and constitutes the bottom of the socket 6 in which armature 5 is reciprocable. In assembling the above noted parts the cup 18 is brazed to the sidewalls of counter-bore 17 in housing 10 so as to effect a vacuum seal between the inside and outside of the switch envelope.

As shown in FIG. 1 the axial extent of coil 14 is preferably such that a portion only of the coil surrounds the end of the cup that extends outwardly from the counterbore 17. The remainder of the coil 14 surrounds a central projection 21 formed in a shoe piece 22 of magnetic material received within bore 13. The enlarged diameter portion 23 of shoe piece 23 is snugly received within bore 13 thus acting as a retainer for coil 14.

For the purpose of holding shoe piece 22 in place a bolt 25 is passed through a locking plate 26 and is rotatably received in a recess 24 in shoe piece 22. Locking plate 26 is held relative to housing 10 by a spring retainer 27 adapted to be snapped into a complementarily formed groove 28 in bore 13 and a nut 29 is positioned on the inner side of plate 26. Upon rotation of bolt 25 in a tightening direction shoe piece 22 is urged inwardly of bore 13 to engage cup 18 and to retain coil 14 in place. Axially extending holes 34 may be provided in shoe piece 22 to receive the leads 31 to coil 14.

Referring again to the socket 6 a cylindrical sleeve 34 is received within the sidewalls of cup 18 and is brazed to said cup so that the inner sidewalls of sleeve 34 provide a continuation of bore 12.

At spaced points around its periphery, sleeve 34 is provided with a plurality of axially extending slots 35 which are adapted to partially receive therein a corresponding number of balls 36. A similar construction is provided at the inner end of bore 12 but in this case a plurality of grooves 38 are formed in housing member 10 at spaced points around bore 12 so as to receive balls 39. In the example shown in the drawings a total of eight balls are employed, four received in slots 35 of sleeve 34 and four received in slots 38 (see FIGS. 3, 4).

The balls 36, 39 do not bear directly on armature 5 but on four spring clips 40 carried by the armature. As best seen in FIGS. 3, 4 each clip is received within a complementarily formed axially extending groove 41 in armature 5. Said clips are preferably of relatively thin spring steel and so formed that their resiliency urges them into engagement with balls 39 at all times. Provision for wear is thus allowed for. Relative movement between clips 46 and armature 5 is prevented by means of a central projection 43 integral with each clip and received in a complementarily formed radially extending hole 44 formed in armature 5. At this point it may be noted that the above described structure provides an effective antifriction bearing for armature 5 and permits the latter to reciprocate freely in socket 6.

It will be understood that coil 14, when energized, urges armature 5 against bottom 19 of cup 18 to open contacts 2, 3. For the purpose of closing contacts 2, 3 a strong helical compression spring 47 is provided at the vacuum end of housing 10 and bears against a spring retainer 48 carried by the tubular element on which movable contact 3 is mounted.

The inner end of housing 10 is provided with a groove 53 for receiving a split retainer ring 51 adapted to be engaged by armature 5 for limiting the movement of the latter outwardly of socket 6. It will be understood, of course, that in normal use of the switch illustrated the engagement of movable contact 3 with fixed contact 2 arrests the movement of armature 5 before the latter engages retainer 51.

An important feature of the present invention resides in the manner in which balls 36 and 39 are retained in operative position and prevented from falling into the unconfined spaces at either end of the armature. It will be noted in this connection that the length of slots 35 is such that the balls as roll between opposite ends thereof during a complete stroke of armature 5. To provide a similar retaining means for balls 39 a radially outwardly projecting lug 55 is formed on each spring clip 40 thereby providing a limit stop for the associated ball-the inner end of grooves 38 providing the opposite limit stop. From the above described structure it will be seen that the balls 36, 39 are adequately caged during shipping or use and cannot be displaced from an operative position.

The operation of the Vacuum switch driving mechanism will be apparent; movable contact 3 is normally held in engagement with fixed contact 2 by spring 47. When it is desired to open the switch, coil 14 is energized to pull armature against the nonmagnetic bottom 19 of cup 18. Upon opening the coil circuit, spring 47 again forces the contact 3 into engagement with contact 2.

It will be noted that the armature 5 and the exterior parts of magnetic material form a magnetic path of variable length and that the length of the path becomes less as the armature moves toward the bottom 19. By this design the power input to coil 14 may be reduced when the vacuum switch is fully open thus reducing heating of the same.

It will be apparent that the above disclosed drive mechanism may be employed with vacuum switches having different modes of operation. For example, a flexible shorting bar may be employed in lieu of contact 3 in which case it may be preferable to assemble the drive mechanism so that retainer 51 does in fact act as a positive limit stop for armature 5.

I claim:

1. In a vacuum switch, a vacuumized envelope, fixed and movable contacts in said envelope, said movable contact being mounted for movement in opposite directions between positions in which the same is respectively engaged and disengaged from said fixed contact, an armature within said envelope and secured to said movable contact, a magnetic coil outside said envelope and adapted to magnetically attract said armature to move said movable contact to one of said positions, and spring means in said envelope for urging said movable contact to the other of said positions, said armature being provided with a plurality of spring clips spaced circumferentially around its periphery, a socket for receiving said armature therein and a plurality of balls interposed between said clips and the sidewalls of said socket for reducing the friction during movement of said armature,

2. In a vacuum switch, a vacuumized envelope, fixed and movable contacts in said envelope, said movable contact being mounted for movement in opposite directions between positions in which the same is respectively engaged and disengaged from said fixed contact, an armatare within said envelope and secured to said movable contact, a magnetic coil outside said envelope and adapted to magnetically attract said armature to move said movable contact to one of said positions, and spring means in said envelope for urging said movable contact to the other of said positions, said armature being provided with a plurality of spring clips spaced circumferentially around its periphery, a socket for receiving said armature therein and a plurality of balls interposed between said clips and the sidewalls of said socket for reducing the friction during movement of said armature, said clips yieldably urging said balls radially outwardly of said armature against said sidewalls of said socket.

3. In a vacuum switch, a vacuumized envelope, fixed and movable contacts in said envelope, said movable contact being mounted for movement in opposite directions between positions in which the same is respectively engaged and disengaged from said fixed contact, an armature within said envelope and secured to said movable contact, a magnetic coil outside said envelope and adapted to magnetically attract said armature to move said movable contact to one of said positions, and spring means in said envelope for urging said movable contact to the other of said positions, said armature being received in a socket for reciprocation therein and adapted to engage the bottom of said socket for limiting movement in one of said directions, a sleeve received in said socket adjacent the bottom thereof and provided with a plurality of axially extending slots therein, said socket being provided adjacent its open end with a plurality of axially extending slots axially aligned respectively with the slots in said sleeves, a plurality of elongated axially extending spring clips carried by said armature with the opposite ends of said clips in registration with the slots in said socket and said sleeve and antifriction balls interposed between said clips and said slots for reducing the friction between said armature and said socket.

References Cited in the file of this patent UNITED STATES PATENTS 1,158,991 Dixon et al Nov, 2, 1915 1,293,052 Dinsmoor Feb. 4, 1919 1,293,697 Canfield Feb. 11, 1919 2,342,527 Bucklen Feb. 22, 1944 2,819,432 Ray Jan. 7, 1958 2,868,922 Leonard Jan. 13, 1959 2,908,780 Walters Oct. 13, 1959 

